The proposed study is the continuation of a long-term investigation of the neuronal, neurochemical, hodological, and synaptic organization of the lateral and basolateral nuclei (ABL) of the rat amygdala. Anatomical studies of the sensory representation within the rat ABL will: 1) delineate the visual, auditory, and somatosensory cortical association pathways directed toward the amygdala; 2) determine the precise areas of termination in the amygdala of unimodal and polymodal cortical association areas as well as thalamic sensory nuclei; and 3) analyze intra-amygdaloid projections from modality-defined ABL domains in order to elucidate the anatomical substrates for sensory convergence. Studies of the chemical neuroanatomy of ABL will: 1) determine the neurotransmitters contained in the major efferent projections of ABL; 2) ascertain neurochemical coexistence patterns in neurons of ABL; 3) analyze the afferent regulation of transmitter levels in ABL neurons containing GABA and peptides; 4) examine the direct afferent innervation of ABL neurons containing GABA and peptides; and 5) determine the ABL cell types that alter gene expression in response to cortical activation. The techniques to accomplish these aims include: 1) the PHA-L anterograde tract tracing technique; 2) techniques that combine transmitter immunohistochemistry (IHC) with PHA-L tract tracing at the light and electron microscopic level; 3) a technique that combines transmitter IHC with HRP retrograde tract tracing; 4) double-antigen IHC; and 5) chemical stimulation and lesioning techniques. Clinical and experimental studies indicate that the amygdala is one of the major forebrain areas involved in emotion and memory. It exhibits significant neuropathology in Alzheimer's disease, is involved in temporal lobe epilepsy, and is one of the major sites of action of the GABA-related benzodiazepine drugs (Valium) and other psychopharmacological agents. The knowledge of the chemical microcircuitry of ABL gained from the proposed study will contribute to an understanding of the anatomy, pharmacology, physiology and pathophysiology of this important brain region.